1. Field of the Invention
The present invention relates to an absorber for causing a liquid working fluid to absorb a gaseous working fluid, and especially to an absorber, which has economical advantages and can improve thermal efficiency in a plant.
2. Description of the Related Art
In general, an interchange of heat between a working fluid and high and low temperature fluids is made in a plant of electric generation by temperature difference, steam power and the like, so as to take power off in a cycle of causing compression, evaporation, expansion and condensation. In a refrigerator and a heat pump, work for the working fluid is done and absorption or emission of heat between the working fluid and the high and low temperature fluids is made in a cycle of compression, evaporation, expansion and condensation.
There has conventionally been proposed a specific cycle in which mixing fluid of fluid such as ammonia having a low boiling point with fluid such as water having a high boiling point is used as the working fluid in order to improve the thermal efficiency in the above-mentioned power cycle or a refrigeration (heat pump) cycle, when there is no substantial difference in temperature between the high temperature fluid and the low temperature fluid.
There is a demand for decreasing a heat transfer area of a condenser as well as an amount of the supplied low temperature fluid to reduce a cost. In view of such a demand, there has been proposed a method in which an absorber is incorporated into the cycle. In the absorber, the liquid working fluid, which has been discharged from an evaporator to be separated once, is caused to absorb vapor of the working fluid, which has been discharged from an expansion device (i.e., a turbine). Latent heat of condensation and heat of absorption during the absorption process are recovered simultaneously by means of the low temperature fluid or the other cooling fluid. Vapor of the working fluid, which has not been absorbed, is supplied to the condenser. Quantity of heat given to the condenser can be decreased in this manner in the above-mentioned method.
An example of the power cycle into which the above-described absorber is incorporated is shown in FIG. 9. FIG. 9 is a schematic descriptive view of the power cycle including the absorber.
The conventional power cycle as shown in FIG. 9 has an evaporator 101 for making a heat exchange between the liquid working fluid and the high temperature fluid to evaporate partially the working fluid, a gas-liquid separator 102 for separating the working fluid going out of the evaporator 101 into a gaseous phase content and a liquid phase content, a regenerator 103 for preheating the liquid working fluid, which has been separated by the gas-liquid separator 102, prior to the entrance of the liquid working fluid into the evaporator 101, a pressure-reducing valve 104 for reducing pressure of the liquid working fluid going out of the regenerator 103, a turbine 105 for causing the gaseous working fluid, which has been separated by the gas-liquid separator 102, to flow and expand to take the power off, an absorber 106 for bringing the gaseous working fluid going out of the turbine 105 into contact with the liquid working fluid going out of the pressure-reducing valve 104, a condenser 107 for condensing the gaseous working fluid of the whole working fluid going out of the absorber 106, a tank 108 for collecting the working fluid going out of the condenser 107 and a pump 109 for imparting a prescribed pressure to the working fluid going out of the tank 108 to supply the working fluid to the regenerator 103 and the evaporator 101.
The conventional absorber is used to cause the liquid working fluid to absorb the gaseous working fluid in a plant such as a chemical plant, a food plant or the like.
Calculation proves that the conventional power cycle having the above-described structure can improve the thermal efficiency in the cycle by causing the liquid working fluid to absorb the gaseous working fluid in the absorber 106. There has however been a problem of incorporating the absorber 106 into the actual plant having the power cycle to make it for practical use.
An object of the present invention, which was made to solve the above-described problems is therefore to provide an absorber, which permits to achieve effective absorption of gaseous working fluid with the use of liquid working fluid, reduce costs of a plant or equipment in which a cycle such as a power cycle including an absorption process is utilized and improve thermal efficiency.
In order to attain the aforementioned object, an absorber of the present invention, in which working fluid including at least two substances having different boiling points from each other is divided into liquid and gaseous phases to supply separately liquid working fluid and gaseous working fluid so as to bring the gaseous working fluid into contact with the liquid working fluid to absorb the gaseous working fluid, comprises:
a shell having a box-shape, said shell having an inside that is divided into at least three zones by at least two parallel partition walls, and said at least three zones locating vertically;
a plurality of wet tubes, said wet tubes comprising tubular bodies each having opposite open ends and two surfaces being opposite in parallel to each other at a prescribed distance, said tubular bodies being disposed in parallel with each other in said shell so that a central axis of each of said tubular bodies coincide with a vertical direction and said surfaces of said tubular bodies are opposite in parallel to each other, said tubular bodies passing through said at least two parallel partition walls so that the opposite open ends of each of said tubular bodies locate in an uppermost zone and a lowermost zone of said at least three zones of the shell, respectively;
a cooling fluid supply portion communicating with the open end of each of said wet tubes to supply a cooling fluid to each of said wet tubes; and
a cooling fluid collection portion communicating with the other open end of each of said wet tubes to collect the cooling fluid in the wet tubes and discharge it outside;
a gap having a prescribed distance being formed between each of upper and lower partition walls of said at least two parallel partition walls, which face an intermediate zone locating between other zones of said at least three zones, on the one hand, and an outer peripheral surface of each of said wet tubes passing through said at least two parallel partition walls, on the other hand; and
(i) the cooling fluid continuously flowing in said wet tubes, while supplying the liquid working fluid from an outside to the zone locating above said intermediate zone so as to be adjacent thereto so that the liquid working fluid continuously flows down from the gap formed between said upper partition wall and said wet tubes along the outer peripheral surface of each of the wet tubes and the liquid working fluid flows through the gap formed between said lower partition wall and said wet tubes to the zone locating below said intermediate zone so as to adjacent thereto and is discharged outside, and (ii) the gaseous working fluid is supplied from the outside to the intermediate zone of said shell so as to come into contact with the liquid working fluid flowing on the outer peripheral surfaces of the wet tubes.
According to the present invention, by providing the wet tubes comprising the tubular bodies in the shell having the box-shape, causing the cooling fluid to pass through the inside of the wet tubes and causing the liquid working fluid to flow down along the outer peripheral surface of the wet tubes so as to make a heat exchange between the working fluid and the cooling fluid through the wet tubes, while supplying the gaseous working fluid into the shell, so as to bring the gaseous working fluid into contact with the liquid working fluid to absorb the gaseous working fluid, it is possible to convert a part of the gaseous working fluid into the liquid working fluid to reduce an amount of vapor to be supplied into the condenser and recover part of heat, which has been used for the heat exchange in the condenser, as heat corresponding to the increased temperature of the liquid working fluid. As a result, the heat transferring area of the condenser can be reduced to make the condenser in a small size. In addition, it is possible to decrease the quantity of heat, which is to be transferred to the cooling liquid in the condenser to discharge outside, thus improving the thermal efficiency of the cycle. The gaps formed between the outer peripheral surface of the wet tube and the partition walls are used as an inlet and an outlet for the liquid working fluid, which is to be supplied into the intermediate zone of the shell, so that an appropriate amount of the working fluid passes through the gap and flows down along the outer peripheral surface of the wet tube. It is therefore possible to ensure the maximum contact area between the liquid working fluid and the gaseous working fluid in a state of permission of making a heat exchange so as to provide an excellent absorption efficiency, thus leading to an easy manufacture of the absorber having a simple structure at low cost.
There may be adopted, as the occasion demands, a structure that each of the surfaces of said wet tubes has a pattern of irregularity, said pattern of irregularity having a common concavo-convex shape to each other and an inverse relationship in concavo-convexities that appear on a working fluid-side and a cooling fluid-side, said concavo-convex shape having a wavy cross section, which extends in a flowing direction of the liquid working fluid in a shape of elongated projections or grooves that are arranged in parallel with each other in a perpendicular direction to said flowing direction by a prescribed pitch.
According to the present invention, by forming on the wet tubes the pattern of irregularity having the concavo-convex shape, which extends in the flowing direction of the working fluid so as to cause the liquid working fluid to flow down along the pattern of irregularity, it is possible to ensure the large heat transferring area and achieve the smooth flow-down of the liquid working fluid to make a stable contact with the wet tubes. It is therefore possible to improve the heat transfer efficiency from the liquid working fluid, which has absorbed the gaseous working fluid, to the cooling fluid through the wet tubes, so as to make a rapid heat transfer, thus permitting more effective absorption of the working fluid, while preventing re-evaporation of the absorbed working fluid.
There may be adopted, as the occasion demands, a structure that a supply port for the gaseous working fluid is formed in said intermediate zone so as to communicate with a lower portion of said intermediate zone and a discharge port for the gaseous working fluid, which has not been absorbed, is formed in said intermediate zone so as to communicate with an upper portion of said intermediate zone.
According to the present invention, by forming the supply port for the gaseous working fluid on the side surface of the shell so as to communicate with the lower portion of the intermediate zone and forming the discharge port for the gaseous working fluid thereon so as to communicate with the upper portion of the intermediate zone, it is possible to make a flow of the gaseous working fluid as an ascending current so that the gaseous working fluid can flow from the upper portion of the intermediate zone to the lower portion thereof, thus forming a countercurrent flow relative to the liquid working fluid flowing down. As a result, an effective heat transfer of the gaseous working fluid to the liquid working fluid can be made without causing loss to improve the thermal efficiency. In addition, it is possible to bring the gaseous working fluid into sure contact with the liquid working fluid, thus improving the absorption efficiency.